Recent studies have defined the alterations in pulmonary surface active material phospholipids during the course of neonatal Respiratory Distress Syndrome (RDS). Using sequential tracheal aspirate analysis for surfactant related phospholipids: phosphatidylcholine, phosphatidylinositol, and phosphatidylglycerol it is possible to define in individual neonates the alterations of the phospholipids during RDS and their response to therapy. Initial studies have suggested that time-related and therapy-related alterations in tracheal aspirate phospholipids can determine postnatal maturation of the lung and response to RDS therapy. This proposal seeks to refine present techniques in tracheal aspirate analysis by quantitating surfactant phospholipids and surfactant specific protein, examining polyphosphoinositides in surfactant, and lung fluid cytology for potential early cellular indices indicating bronchopulmonary dysplasia. Tracheal aspirate material is a pulmonary effluent readily and routinely obtainable in neonates with lung disease requiring ventilatory support. Careful study of this material should provide information concerning the reparative capability of the neonate as well as provide additional biochemical and cellular indices of RDS. Additional studies on infants developing bronchopulmonary dysplasia should aid in the elucidation of its pathogenesis and provide additional biochemical and cytologic measures of the serverity and recovery from this disorder.